Apparatus for catalytically decontaminating exhaust gases and method for producing the apparatus

ABSTRACT

An apparatus for catalytically decontaminating exhaust gases, preferably for motor vehicle engines, includes a metal carrier body having a plurality of corrugated, or smooth and corrugated, sheet metal layers. The sheet metal layers have smooth end segments overlapping one another and being disposed as an outer layer on the periphery of the metal carrier body. A jacket encompasses the metal carrier body. At least one weld seam may simultaneously connect the smooth end segments to one another and to the jacket. A mechanical retaining device may form-lockingly secure the metal carrier body in the axial direction in the jacket while engaging an end surface of the outer layer. A method for producing the apparatus includes initially coating individual corrugated, or smooth and corrugated, sheet metal layers of a metal carrier body with a wash coat, except for uncoated regions of lengthened smooth end segments of the sheet metal layers overlapping one another and being disposed as an outer layer on the periphery of the metal carrier body. The sheet metal layers are intertwined and inserted into a jacket encompassing the metal carrier body. The sheets are simultaneously connected to one another and to the jacket in the uncoated regions of the lengthened, smooth end segments resting on one another with at least one weld seam.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 08/138,342, filedOct. 18, 1993, now U.S. Pat. No. 5,366,700, which is a Continuation ofInternational Application Serial No. PCT/EP92/00796, filed Apr. 8, 1992.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus for catalytically decontaminatingor detoxifying exhaust gases, particularly for motor vehicle engines,having a metal carrier body including a plurality of layers ofcorrugated, or smooth and corrugated, sheet metal, and a jacket thatencompasses the metal carrier body and is connected to it by weldingtechniques.

It is known from German Published, Non-Prosecuted Application DE-OS 2720 322 to weld metal foils of a metal catalytic converter with electronbeams. The individual layers of sheet metal are welded together in sucha way that the metal catalytic converter is joined to make anintrinsically rigid insert. The insert is secured in a housing, forinstance once again by electron beam welding.

It is known from German Published, Non-Prosecuted Application DE-OS 2727 967 (which is a continuation of German Published, Non-ProsecutedApplication DE-OS 27 20 322) to produce the metal catalytic converter bymeans of laser welding.

It is known from Published European Application No. 0 245 737 A1,corresponding to U.S. Pat. Nos. 4,803,189; 4,832,998; 4,923,109; and4,946,822, to form honeycomb bodies of corrugated and smooth sheet metallayers in such a way that the corrugated sheets have straight sectionson their ends which extend approximately centrally between the adjoiningsmooth sheets. The ends of the corrugated sheets must not touch the endsof the smooth sheets and they each rest individually on an encompassingjacket or casing tube, with which they are joined by joining techniques.

A disadvantage of the above-mentioned structures is that very thin metalfoils (0.05 mm, for instance) are joined, particularly welded, to ahousing that is multiple times thicker. In order to achieve a durableconnection between the metal catalytic converter and the housing, thewelding depth of an electron or laser beam must be adjusted veryprecisely, because otherwise the welded connection between the housingand the metal catalytic converter becomes unstable, or else the outerfoil layer of the metal catalytic converter will be cut apart.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide an apparatus forcatalytically decontaminating exhaust gases, which overcomes thehereinafore-mentioned disadvantages of the heretofore-known devices ofthis general type and which has a metal carrier body with a honeycombbody which can be axially fixed simply and durably in a jacket, and inparticular can be welded in place.

With the foregoing and other objects in view there is provided, inaccordance with the invention, an apparatus for catalyticallydecontaminating exhaust gases, preferably for motor vehicle engines,comprising a metal carrier body having a periphery and having aplurality of corrugated, or smooth and corrugated, sheet metal layers atleast some of which being corrugated, the sheet metal layers havingsmooth end segments overlapping one another and being disposed as anouter layer on the periphery of the metal carrier body; a jacketencompassing the metal carrier body; and at least one weld seamsimultaneously connecting or joining the smooth end segments to oneanother and to the jacket.

In accordance with another feature of the invention, the outer layer isbetween 0.5 mm and 2 mm thick.

The proposed embodiment enables secure joining of the metal carrier bodyto the jacket. The outer layer of the metal carrier body, which isformed of overlapping smooth end segments of the corrugated, orcorrugated and smooth, sheet metal layers, brings about an accumulationof material at the periphery of the metal carrier body that permitssimple welding of the metal carrier body to the jacket. The smooth endsegments of the sheets are approximately identical in length. Due totheir uniform distribution over the periphery, they are spaced uniformlyapart from one another where they penetrate the outer layer of the metalcarrier body, from which they extend radially outward and finally cometo an end at the surrounding jacket. This assures that each sheet metallayer is joined directly to the jacket. The thickness of the outer layeris selected in such a way that it is greater than the wall thickness ofthe surrounding jacket.

In accordance with a further feature of the invention, the outer layerof the metal carrier body is welded to the jacket through the jacket.The welding depth for such through welding through the jacket into theouter layer of the metal carrier body is adjusted in such a way that thewelding penetrates radially inward to approximately two-thirds of thethickness of the outer layer. If the welding depth fluctuates, anadequate tolerance range still remains, so that the outer layer of themetal carrier body is welded to the jacket if the welding depth is less,but is not cut through if the welding depth is greater.

In accordance with an added feature of the invention, the at least oneweld seam is a laser weld seam. The welding process is not limited tolaser or electron beam welding. Other welding processes, such as TIG(tungsten inert gas) or arc welding, can be used, although by laserwelding to produce a weld seam, an especially advantageous and inparticular fast production option is afforded.

In accordance with an additional feature of the invention, the outerlayer of the metal carrier body has an end surface on which the jacketis welded. Once again, the great material thickness of the outer layeris especially advantageous. For example, it is possible for the metalcarrier body to be welded to the jacket on its end-surface lines ofcontact by means of a fillet weld, if the jacket protrudes, and by meansof a V seam, if the jacket ends flush with it. Any familiar methods mayused as the welding process.

In accordance with yet another feature of the invention, the outer layerhas end surfaces being peeled away from the metal carrier body, or beingpushed away from the metal carrier body by deformation, forming acollar-like rim and the collar-like rim is welded to the jacket. In thiscase the outer layer of the metal carrier body is peeled off outward incollar-like fashion, producing an outwardly protruding rim that ends atthe end surface of the jacket and is joined to it by welding, forinstance spot or TIG welding. At the same time, a tube, cone or the likeon the end opposite the jacket, may be welded jointly to the collar-likerim and the jacket.

With the objects of the invention in view, there is also provided anapparatus for catalytically decontaminating or cleaning exhaust gases,preferably for motor vehicle engines, comprising a metal carrier bodyhaving a periphery and having a plurality of corrugated, or corrugatedand smooth, sheet metal layers, the sheet metal layers having smooth endsegments overlapping one another and being disposed as an outer layer onthe periphery of the metal carrier body, the outer layer having an endsurface; a jacket encompassing the metal carrier body; and mechanicalretaining means form-lockingly securing the metal carrier body in theaxial direction in the jacket and engaging the end surface of the outerlayer.

Since these retaining means engage the outer layer at the end surface,the retaining forces that must be brought to bear for fixing the metalcarrier body in the jacket are transmitted to all of the sheet metalplies of the outer layer. Since the smooth end segments on the peripheryof the metal carrier body overlap without any notable gap between them,the pressure per unit of surface area that results from the retainingforces is markedly reduced as compared with conventionally producedapparatuses for exhaust gas cleaning.

The mechanical retaining means may be constructed in various ways. Forinstance, a supporting ring for supporting the metal carrier body can beinserted into the jacket and welded, brazed or press-fitted into it. Themechanical retaining means may also be achieved by drawing-in the jacketor stamping retaining tabs out of the jacket upstream of the endsurfaces of the metal carrier body. Depending on the conditions of use,it is possible to combine these and other options. An embodiment of themechanical retaining means in the form of converging or diverging cones,which are typically mounted upstream and downstream of an apparatus forexhaust gas cleaning, is especially advantageous. In this case the conesmay be constructed in such a way that their outside diameter matches theinside diameter of the jacket of the exhaust gas cleaning apparatus.They are inserted into the jacket and joined to it, preferably bywelding, whereupon the end surfaces of the cones rest on the endsurfaces of the metal carrier body in the region of the outer layer.

With the objects of the invention in view, there is additionallyprovided a method for producing an apparatus for catalyticallydecontaminating exhaust gases, preferably for motor vehicle engines,which comprises initially coating individual corrugated, or smooth andcorrugated, sheet metal layers of a metal carrier body with a wash coat,except for uncoated regions of lengthened smooth end segments of thesheet metal layers overlapping one another and being disposed as anouter layer on the periphery of the metal carrier body; intertwining thesheet metal layers and inserting the intertwined sheet metal layers intoa jacket encompassing the metal carrier body; and simultaneouslyconnecting the sheets to one another and to the jacket in the uncoatedregions of the lengthened, smooth end segments resting on one anotherwith at least one weld seam.

In this case, coated, corrugated, or corrugated and smooth, sheet metallayers are used, having smooth end segments which are uncoated in aregion that is layer to be welded to the jacket. The coating, such as awash coat, is applied to the semifinished product prior to furtherprocessing to make the exhaust gas cleaning apparatus. A smooth endsegment of the sheets is either shielded, so that an uncoated regionremains there, or else the entire sheet is coated, and the region issubsequently freed of the coating by a chemical or mechanical process.Mechanical removal of the coating could be performed by brushing the endsegments with bristles, for instance.

In this method, it is especially advantageous that the finished metalcarrier body need not be coated afterward, but rather is alreadyassembled from coated sheets. This results in a uniform distribution ofthe coating on the corrugated and smooth sheet metal layers, and inparticular accumulations of material, which in the case of subsequentcoating develop in the corners between the lines of contact of thecorrugations of the corrugated sheets with the smooth sheets, areavoided. In the exhaust gas cleaning apparatus, the effective surfacearea is greater and the pressure drop is less as a result.

The invention as defined by the features and steps recited above canadvantageously be employed for carrier bodies of the kind in which aplurality of plies extend from the inside outward, or in other words inaccordance with German Patent DE 40 16 276 C1 or Published EuropeanApplication No. 0 245 736 A1, for instance.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin an apparatus for catalytically decontaminating exhaust gases and amethod for producing the apparatus, it is nevertheless not intended tobe limited to the details shown, since various modifications andstructural changes may be made therein without departing from the spiritof the invention and within the scope and range of equivalents of theclaims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, fragmentary, diagrammatic view of a portion I ofFIG. 2 with smooth end segments at a jacket;

FIG. 2 is a plan view of a metal carrier body in the jacket;

FIG. 3 is a perspective view of a metal carrier body in the jacket withan encompassing zig-zag weld seam;

FIG. 4 is a view similar to FIG. 3 of a metal carrier body in the jacketwith two weld seams encompassing it in a straight line;

FIG. 5 is a fragmentary, sectional view through a metal carrier body anda jacket with through-welding in the jacket and an outer layer;

FIG. 6 is a fragmentary, sectional view through the metal carrier bodyand the jacket with a fillet weld at the jacket and the outer layer;

FIG. 7 is a fragmentary, sectional view through the metal carrier bodyand the jacket with an end-surface weld seam at the jacket and the outerlayer;

FIG. 8 is a fragmentary, sectional view through the metal carrier bodyand the jacket with a collar-like rim and an encompassing weld seam onthe jacket and the collar-like rim;

FIG. 9 is a fragmentary, sectional view through the metal carrier bodyand the jacket with mechanical retaining means; and

FIG. 10 is an enlarged, fragmentary view of a portion of FIG. 2 withcoated sheets and uncoated, smooth end segments at the jacket.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is seen a portion of theapparatus according to the invention. Corrugated sheet metal layers 4are provided with smooth end segments 5. These end segments 5 arestacked in alternation with smooth end segments 5' of sheet metal layers3 that are smooth or are provided with corrugations, such asmicrocorrugations, to make an outer layer 8 of a metal carrier body 1that is seen overall in FIG. 2. The end segments 5, 5' are ofapproximately equal length, so that on the condition of an introductionof the smooth end segments 5, 5' into the outer layer 8 with theintroduction being distributed uniformly over the periphery of the metalcarrier body 1, each end segment 5, 5' comes into contact with asurrounding jacket or casing 2 and can be welded to it. Lengthening thesmooth end segments 5, 5' brings about an increase in thickness of theouter layer 8, because as a result the number of smooth end segments 5,5', which are stacked at the same time into the outer layer 8 at onepoint along the periphery of the metal carrier body 1, increases.

The smooth end segments 5, 5' conform very well to the encompassingjacket 2, so that no voids of significant size remain at the pointswhere one of the end segments 5, 5' ends and the end segment 5', 5located below it comes into contact with the jacket 2. Due to theintrinsic tension of the sheets 3, 4, the outer layer 8 is pressedagainst the enveloping jacket 2. Therefore, there is no need foradditional securing provisions for retaining the metal carrier body 1 inthe jacket 2 prior to the welding.

FIG. 2 shows a preferred embodiment of an apparatus for exhaust gascleaning, which contains the metal carrier body 1 of the invention thatis shown on a larger scale in FIG. 1. In this case, four stacks ofstacked sheets 3, 4 with smooth end segments 5 are placed crosswiseagainst one another and are intertwined together in the same directionto form a round metal carrier body 1. In the process, the outer layer 8is formed by the stacking of the smooth end segments 5, 5'. The metalcarrier body 1 is inserted into the jacket 2 and welded to it. Thespring force of the sheets 3, 4 has the effect of not requiring thesheets 3, 4 of the metal carrier body 1 to be joined to one another byjoining techniques.

FIG. 3 shows a variant embodiment of the apparatus. The metal carrierbody 1 of FIG. 3 is inserted into a tubular jacket 2. The outer layer 8of the metal carrier body 1 is welded to the jacket 2 through the jacket2. A weld seam 6 extends in zig-zag fashion over the periphery of thejacket 2. The weld seam 6 may be produced by laser welding, forinstance. To that end, the tubular jacket 2 that is equipped with themetal carrier body 1 is set into rotation about its longitudinal axis,for instance, and is moved into a laser beam that executes anoscillating motion in the direction of the motion of the longitudinalaxis of the jacket 2. The energy of the laser beam brings about throughwelding of the jacket 2 all the way into the outer layer 8.

FIG. 4 shows a further variant of the apparatus. In this case the metalcarrier body 1 is joined to the jacket 2 by two weld seams 6 extendingaround the periphery in a straight line. The weld seams 6 are producedby TIG (tungsten inert gas) welding. For instance, the apparatus is setinto rotation about its longitudinal axis and put into contact with twoTIG welding electrodes.

FIG. 5 shows a section through the jacket 2, the metal carrier body 1with its outer layer 8, and a weld seam 6. The weld seam 6 is producedby through welding. The weld seam 6 extends through the jacket 2 as faras entering into the outer layer 8 and fixes the smooth ends 5, 5' ofthe sheets 3, 4 to the jacket 2. At least two smooth end segments 5, 5'are always welded to the jacket 2 in that case.

FIG. 6 shows a section through an apparatus in accordance with anotherembodiment of the invention. The jacket 2 protrudes past the metalcarrier body 1, so that the weld seam 6 can be placed in the form of athroat groove in the corner that results at the end surface of the metalcarrier body 1 and the inner wall of the jacket 2. The weld seam 6 ismade in such a way that the outer layer 8 of the metal carrier body 1 iswelded to the jacket 2. The weld seam 6 can be produced by an arbitrarywelding method, for instance by electrowelding or laser welding.

FIG. 7 again shows a section through an apparatus in accordance with asimilar embodiment of the invention. In this case, however, the metalcarrier body 1 and the jacket 2 are flush at their end surfaces. Thus aweld seam 6 in the form of a U-shaped or V-shaped groove can besimultaneously welded from the end surface vertically into the jacket 2and the outer layer 8 of the metal carrier body 1. Once again, thewelding method is arbitrary.

The width of the weld seam 6 with which an apparatus of this embodimentis welded will be selected in such a way that it is narrower than thethickness of the outer layer 8 and the jacket 2 taken together, as isshown in FIGS. 6 and 7.

FIG. 8 shows a section through a further embodiment of the invention.The outer layer 8 is peeled off from the metal carrier body 1 on theoutside in collar-like fashion in the end-surface region and then restson the end surface of the jacket 2. The outer layer 8 is welded to thejacket 2, with welding being performed on the end surface into the outerlayer 8 in the region of a collar-like rim 7 and on the periphery intothe jacket 2. The collar-like rim 7 is cut away from the metal carrierbody by a suitable tool and at the same time is bent outward or merelybent outward in a shaping manner. In particular, the tool may be theelectrode of a spot welding unit, and the weld seam 6 may be producedduring the peeling or deforming process by means of spot welding. Theconnection between the metal carrier body 1 and the jacket 2 inaccordance with claim 6 is performed in a material-locking or integraland a form-locking manner. A form-locking connection is one whichconnects two elements together due to the shape of the elementsthemselves, as opposed to a force-locking connection, which locks theelements together by force external to the elements.

In FIG. 9, a section is shown through an apparatus for exhaust gascleaning in accordance with an additional embodiment of the invention.In this case the metal carrier body 1 is inserted into the jacket 2. Thesmooth end segments 5 of the smooth and corrugated sheets 3, 4 form theouter layer 8. Mechanical retaining means 9 in the form of a tubularsegment is inserted into the jacket 2. The mechanical retaining means 9rest on the end surface of the metal carrier body 1 in the region of theouter layer 8 and are joined to the jacket by an end-surface weld seam6. The metal carrier body 1 is form-lockingly fixed in the jacket 2 inthe axial direction.

FIG. 10 shows a portion of a metal carrier body that was produced by themethod of the invention. In this case corrugated sheet metal layers 14and smooth sheet metal layers 13 are provided with a coat, for instancea wash coat 10, 10' which was already applied previously to theindividual sheet metal layers. Smooth end segments 15, 15' of the sheetmetal layers 13, 14 are uncoated in a region A, which is equivalent tothe length of the smooth end segments 15, 15' in this case. The smoothend segments 15, 15' are stacked to make an outer layer 18 that rests ona jacket 12. The jacket 12 and the outer layer 18 are joined by joiningtechniques through the use of a weld 16, which is possible only if theend segments are bright, clean or plain and uncoated.

We claim:
 1. A method for producing an apparatus for catalytically decontaminating exhaust gases, which comprises:a) providing individual at least partly corrugated sheet metal layers of a metal carrier body coated with a wash coat and having end segments; b) intertwining the sheet metal layers, overlapping end segments of the sheet metal layers, and inserting the intertwined sheet metal layers into a jacket encompassing the metal carrier body; and c) simultaneously connecting the overlapping end segments of the sheet metal layers to the jacket in uncoated regions of the end segments with a joining technique.
 2. The method according to claim 1, which comprises forming the metal carrier body from a plurality of corrugated sheet metal layers.
 3. The method according to claim 1, which comprises forming the metal carrier body from a plurality of smooth and corrugated sheet metal layers.
 4. The method according to claim 1, wherein step a) comprises primarily completely coating the sheet metal layers with a wash coat and subsequently freeing the end segments of the sheet metal layers of the coating.
 5. The method according to claim 4, wherein the freeing step comprises a chemical process step.
 6. The method according to claim 4, wherein the freeing step comprises a mechanical process step.
 7. The method according to claim 4, wherein the freeing step comprises brushing the coating from the sheet metal layers.
 8. The method according to claim 1, wherein step c) comprises connecting the sheets to the jacket with at least one weld seam.
 9. The method according to claim 1, wherein the end segments of the sheet metal layers with uncoated regions are disposed as an outer layer on a periphery of the metal carrier body. 